Remember when I said that, to him, a reflection was simply that? I misspoke. “Can I have some privacy?” he will say as he clambers onto the bathroom counter and opens the mirrored cabinet doors so that they touch his cheeks. He is talking to his friends, his twins, learning about infinity.

(“Susan, do you have any twin sisters?” he asked me the other night at dinner, and I said, “No, I don’t think so” — but if he only knew for how long and how much I wanted a twin sister, lived with the hope that one might, despite my own mother’s flat denials, miraculously appear, long-lost. If only he knew of the reams of foolscap I devoted to twin-sister short stories, not to mention a 40-page novella that my father took to work and got his secretary to type on an IBM Selectric. But I digress.)

Perhaps it’s no coincidence that we have been reading, of late, some Lewis Carroll: Rachel’s childhood copy — actually, make that Rachel’s mother’s childhood copy — of Alice’s Adventures in Wonderland and Through the Looking Glass. “To Wendy, With love from Nan. Christmas 1949,” the book is inscribed. Just below that inscription, Wendy wrote her name, in full, on a fancy bookplate (“This book belongs to...”). And then, just in case, she wrote it again, on the title page, along with her address. A generation later, Rachel’s name and address — and phone number — were painstakingly etched out in pencil opposite her mother’s. All of which by way of saying: Don’t lose this. This is valuable.

Rowan plays and plays and plays, acting out elaborate scenarios with trains and trucks and Bakugans and the faces and the spaces beyond them in the mirror. The borders of his world are still, utterly permeable, open to possibility. And for this I am grateful. Don’t lose this, I want to tell him: This is valuable.